Although this build can be used in both PvE and PvP, make no mistake that it is the single most challenging version of Sniper to use effectively. A lucky string of DoT crits will fill your energy bar. An unlucky lack of crits if you don't have Adrenaline Probe available (and trust me, the cooldown reduction is essential!) will break you.
Cover and Cull (16/2/23)
So you want to kill things really, really fast and use Cull almost continuously? I had to take every possible energy regeneration skill to manage it but -- this is probably the build you want.
- Very high sustained damage (probably the highest sustained damage potential of any Sniper spec in the game). I find it's much easier to put up WZ numbers with this spec than with my pure Marksmanship build and that there is a noticeable difference in Operations encounters.
- Good against armored targets (i.e. HM/NM bosses) because most of its damage is internal; I'd predict this has about 2-3% more damage than my normal Marksmanship build.
- It is possible to use this build in Operations and Hard Modes if you aren't yet geared in order to make up your damage (which is what I did). After I got my gear I switched back to my 31/7/3 Marksman.
- This build can be played in PvP but I wouldn't suggest it. It's designed for PvE raiding. Nothing takes down bosses faster than this build -- though you may or may not have fun beating on tanks with this one.
- Insanely difficult energy management. You have to be totally focused on what you're doing and, although it is more damage, it is only about 2-3% more damage than a pure Marksmanship PvE build.
- Weird, weird playstyle and rotations. Do not attempt this build unless you are intimately familiar with Marksmanship. Be prepared for energy management to challenge you.
- There is almost no room for modification in this build. You MUST have Sniper's Nest in Marksmanship, you MUST have Energy Tanks from Engineering, and you MUST have Lethal Purpose in Lethality.
There's a reason I call this build "Cover and Cull." You are essentially playing a Marksmanship sniper with Cull replacing Followthrough as your primary source of damage. You follow a normal "sustained" Marksmanship rotation until Cull is off cooldown (when using it takes priority). You need to stay in cover to get the energy regeneration bonus from Sniper's Nest. I cannot stress how essential this is. The good thing about this build is that you can use Cull out of cover if you need to move, and your DoTs keep ticking while you're moving.
This is literally the only "functional" hybrid I've found capable of doing comparable damage to a pure Marksmanship build (which is my gold standard for comparison).
In practice you are now a two-phase Sniper. You have a Marksmanship phase (Snipe, Series of Shots, Ambush) for sustained damage in order to manage your energy. You also have a Lethality phase (Corrosive Dart, Corrosive Grenade, Cull) in order to hammer the boss.
YOU MUST STAY IN COVER UNLESS YOU ARE AVOIDING BOSS MECHANICS. THIS BUILD WILL NOT WORK WITHOUT SNIPER'S NEST REGEN.
First you put your DoTs on and then you Cull the target (while in cover!). After that you start playing like a normal Marksmanship sniper. You don't really lose any energy while you're doing this because Marksmanship is so efficient. While you're waiting on the 9s CD of Cull to wear off, you should be using abilities like Ambush and Series of Shots -- things with long channels that regenerate most of their energy while you're doing damage. Try to stay in 5/6 ticks of energy.
You need to try to sit in one spot and keep your DoTs up.
You also want to use Adrenaline Probe before your energy bottoms out! That means using it at 30-40% of your max energy pool in order to get straight back up into max energy regen without waiting. If you use the probe when you're drained, you'll only end up with moderate energy regen.
This build keeps Adrenaline Probe on a fairly forgiving 1:30 CD. It's still possible to mess up.
The key in PvP is to get your Corrosive Grenade on as many targets as you can in order to increase the likelihood that you'll get DoT crits to regenerate energy.
It's possible to get a lucky string of DoT crits and end up with something crazy like 10/tick energy regen. Unfortunately it is also possible to get no crits even if you have four DoTs on your target. You need to be prepared for both possible outcomes.
It works and it does a lot of damage. I'd even venture to say this build does more sustained damage than my pure Marksmanship PvE raiding build -- the one I'm using right now. However, it's massively challenging to manage the energy requirements. It can be done, right? But I wouldn't call it a fun thing to do if you're also focusing on boss mechanics.
I still prefer using a pure 31/7/3 Marksmanship build in practice (this is the one I post in my guide), but this 16/2/23 build was surprisingly effective.
I figured I'd toss it out there for those of you who might like to try something different.